1. Field of the Invention
This invention relates to rotatable grips for actuating a derailleur-type bicycle gear shifting system. More particularly, it relates to handlebar-mounted rotatable grips designed to ergonomically fit the joints and lands of a rider's hand.
2. Description of Related Art
Hand-rotatable bicycle gear shifters have been developed as replacements for older lever-actuated shifters, especially for use in conjunction with off-road or "mountain" bicycles. Hand-rotatable shift actuators are disclosed, for example, In U.S. Pat. No. 4,900,291 issued Feb. 13, 1990; U.S. Pat. No. 4,938,733 issued Jul. 3, 1990; U.S. Pat. No. 5,102,372 issued Apr. 7, 1992; and U.S. Pat. No. 5,476,019 issued Dec. 19, 1995. All of these patents are assigned to the assignee of this application. In each of the foregoing patents, a bicycle derailleur is actuated by a rotatable grip which is located on the handlebar of the bicycle inboard of a customary stationary handgrip. Prior to this invention, the gripping surface of rotatable grips sold by the assignee of this application was typically formed of foam rubber or neoprene and had a smooth outer surface, as shown in FIGS. 33 and 40 of U.S. Pat. No. 5,102,372 and FIGS. 21 and 40 of U.S. Pat. No. 5,197,927 reference above.
The assignee has experimented with hand-rotatable grips with axially extending ribs where the grips were formed of a hard plastic material such as ABS; these grips were less than optimal in that they presented harsh sharp edges to the operator's hand. These edges were uncomfortable to the rider, presenting an especially acute problem during jarring off-road bicycle riding over uneven surfaces and obstacles. Also, these prior rotatable grips of the assignee tended to become slippery when fouled by mud and the like, reducing the amount of torque capable of being applied by the rider and requiring the rider to exert a greater gripping force on the shifters. A need therefore exists for improved grips with optimum torque-transmission and anti-fouling features which are adapted to be incorporated into a hand-rotatable gear shifter.